1. Field of the Invention
The invention concerns heatsinks which remove the heat dissipated by electronic components.
2. Description of the Prior Art
Electronic components such as transistors, thyristors, triacs, diode bridges and other components dissipating a significant quantity of heat are cooled by placing them on heatsinks which are not mounted on the electronic circuit board carrying the other components of a circuit. The components are then connected to the board by wires. The heatsinks may be large and fixed to the outside of an equipment casing, to its rear panel, for example.
If components cannot be remotely mounted, room must be provided on the electronic circuit board for mounting the heatsinks. This applies, for example, to integrated circuits dissipating a few watts, such as semi-custom application-specific integrated circuits (ASIC). It may also apply to passive components such as power resistors which cannot be remotely mounted or where this is to be avoided, for example to avoid the use of connecting wires.
The heatsinks used for this purpose usually occupy a considerable amount of space on the board.
Also known are heatsinks designed to mount directly on the integrated circuit to be cooled, in order to reduce their size. German patent application No 32.03.609 in the name of SIEMENS describes an integrated circuit heatsink of this kind. It comprises a plate bent to a U-shape whose central part is applied to the upper surface of integrated circuit, the lateral parts of the U-shape plate comprising extensions parallel to the lateral parts ending in fixing lugs. The fixing lugs are soldered with leads of the integrated circuit to the printed circuit board on which the integrated circuit is mounted. With this kind of heatsink the amount of room used up on the board is reduced because the heatsink is mounted on the component to be cooled.
The main drawback of this heatsink is that the surface in contact with the integrated circuit is flat so that there is the risk of poor cooling if the integrated circuit is not correctly positioned on the printed circuit board, in other words if its upper surface is not parallel to the board. It is therefore necessary to check that the integrated circuit is positioned correctly, which is costly, difficult and may even be impossible if the components are wave soldered.
This type of heatsink is also suitable only for integrated circuits dissipating a small amount of heat, because of the limited surface area of the heatsink. It is not possible to increase this surface area to dissipate more energy because of the resulting overall height. Also, small integrated circuits, for example eight-pin integrated circuits, are cooled less effectively because the dissipation area is reduced.
Each heatsink of this type is specifically designed for a particular size of integrated circuit and it is therefore necessary to stock a large number of different heatsinks.
An object of the present invention is to remedy these drawbacks.
To be more precise, one object of the invention is to provide a heatsink for electronic components mounted on a circuit board which has optimal thermal contact with the components to be cooled, irrespective of their position on the circuit board, and compact overall dimensions.
Another object of the invention is to provide a heatsink of this kind which is of low cost and optimally cools any type of component irrespective of its size.